1. Field of the Invention
The present invention relates to knee arthroplasty, and, more particularly, to surgical methods and a tibial implant for accommodating the anterior cruciate ligament during unicompartmental or bi-unicompartmental knee arthroplasty procedures.
2. Description of the Related Art
Unicompartmental knee arthroplasty and bi-unicompartmental knee arthroplasty procedures involve replacing damaged articular surfaces of a knee joint, while retaining at least the central compartment and the cruciate ligaments. The benefits of both compartmental procedures include the availability of minimally invasive procedures, quicker recovery, and retained knee kinematics compared with total knee arthroplasty procedures.
During a unicompartmental knee arthroplasty procedure, repairs may be made to either the medial compartment or the lateral compartment of the knee, while retaining the other side compartment, the central compartment, and the cruciate ligaments. This procedure requires resection of either the medial compartment or the lateral compartment.
During a bi-unicompartmental knee arthroplasty procedure, repairs may be made to both the medial compartment and the lateral compartment, while still retaining most of the central compartment and the cruciate ligaments. This procedure requires resection of both the medial and lateral compartments. Also, in some cases, a portion of the central compartment is resected to bridge the resected medial and lateral compartments.
The knee joint includes the anterior cruciate ligament (ACL) and the posterior cruciate ligament (PCL). The ACL controls hyperextension of the knee. As the knee joint is positioned in extension, the ACL tightens and functions to prevent hyperextension of the knee. The ACL runs from the posterior side of the femur to the anterior side of the tibia. More specifically, the ACL runs from the posterior side of the femur to a spinous process on the anterior side of the tibia. The spinous process is primarily centered on the proximal tibia, but it also extends into the medial and lateral compartments of the proximal tibia.
Current resection methods often result in removing a significant portion of the spinous process to which the ACL attaches. Generally, enough of the spinous process remains to maintain ACL attachment. However, the strength of the remaining spinous process is significantly undermined, so much so that when the ACL of a knee arthroplasty patient tightens, the spinous process may crack or even break away from the tibia.